Freedom R8100 SERIES, Operator'S Manual

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Figure 2.2.7.9.1.4-2 HCPM Frequency Constellation
Frequency Counter (Standard Test Mode Meter Zone selection)
The Frequency Counter can be used to measure the transmitter symbol rate accuracy error, the difference
of the actual minus the ideal. Thus a positive error indicates that the transmitter clock is too fast. P25 phase
2 standard TIA-102.CCAB-A 3.2.14 Symbol Rate Accuracy states that the symbol rate error shall not
exceed 10 PPM which is +/- 60 mHz given the ideal symbol rate of 6000 baud. The transmitter should be
transmitting the high deviation pattern (+3,+3,-3,-3) whose frequency period is a quarter of the baud rate
period. The R8100 should be configured with optimal settings (i.e. RF Zone: Modulation = FM,
Bandwidth = 12.5 kHz; Audio Zone: High Pass Filter = 300 Hz, Low Pass Filter = 3 kHz). See 2.2.5.5 for
an FM rate measurement. Use the following equation to compute the error: ppm error =
(Frequency_Count
Hz
/1500 - 1)*10
6
, e.g. (1500.0015/1500-1)*1000000 = 1 PPM.